http://localhost/xmlui/handle/123456789/1292 2026-05-22T04:31:17Z http://localhost/xmlui/handle/123456789/7004 Assessment of the Sources and Hydrological Impacts of Best Management Practices on Pollutants Flow Using SWAT in Nyangores River of Upper Mara Basin, Kenya Kigira, Francis Karanja The Nyangores River watershed, located in Kenya's upper Mara Basin has challenges of rivers degradation, where increased non-point source pollution has caused water quality issues. The objectives were identify the key sources of pollutants, calibrate and validate the SWAT model for streamflow, sediment, and nutrient transport and to assess the impact of various Best Management Practices (BMPs) on nutrient and sediment loads. Data collection followed: gathering hydro-climatic data for model calibration, field observations, collecting samples and laboratory analysis. Impacts of various BMP scenarios on water quality were modelled, focusing on riparian buffer zones, reforestation, and contour farming. Calibration and validation with indicators such as the Nash-Sutcliffe Efficiency (NSE) and R² was done for reliability. Parameters tested, Ph., Ec, Nitrates, Phosphates and Total suspended solids (TSS).Nitrogen levels in the river exceeded safe limits by 50%, with average concentrations of 3.2 mg/L, while phosphorus levels were recorded at 1.1 mg/L, surpassing the eutrophication rate which is TP 0.05mg/L and TN 1.0mg/L. Sedimentation contributed to a 35% increase in total suspended solids (TSS), with average TSS levels measured at 210 mg/L, particularly in areas with steep slopes and poor soil conservation practices. The SWAT model was calibrated using streamflow data from 2003-2008, and the calibration process achieved satisfactory results, with a Nash-Sutcliffe Efficiency (NSE) of 0.72 and an R² value of 0.75. During validation, the model performance well with an NSE of 0.70 and an R² of 0.73 for the validation period (2009-2013) demonstrating the effectiveness of the model. Nitrogen and phosphorus was reduced by 38% and 42% in simulation. In conclusion, this research demonstrates the SWAT model's efficacy in Nyangores watershed, advocating for sustainable land management practices to mitigate water pollution and emphasizing the importance of preserving natural ecosystems for water quality protection. The study recommends preserving natural forests as they effectively control pH, electrical conductivity, nitrates, and phosphates compared to grasslands. Management practices, such as filter strips and contouring, resulted in reduced sediment yields. Public awareness on the importance of management practices and riparian vegetation is paramount. PhD in Soil and Water Engineering 2026-05-21T00:00:00Z http://localhost/xmlui/handle/123456789/6995 Effect of Black Soldier Fly Larvae Meal Inclusion in Layer Feeds on the Quality of the Eggs Mwangi, James Kamothoi The high cost of fish meal (FM), a conventional protein source in poultry feeds, presents a major challenge especially for the small-scale farmers. Black soldier fly larvae meal (BSFLM) is a promising nutrient rich alternative, but its effect on egg quality requires comprehensive evaluation. The current study aimed to provide the first comprehensive evidence of the nutrient quality of eggs harvested from layers fed diets containing black soldier fly larval meal (BSFLM) as a substitute for the fish meal (FM). This study utilized seventy-five Isa Brown layers (n-75) fed on BSF-based diet types that were nutritionally balanced consisting of 0% BSFLM+100% FM - (control); 25% BSFLM+75% FM; 50% BSFLM+50% FM; 75% BSFLM+25% FM and100% BSFLM+0% FM). The research employed a completely randomized design (CRD) model, with the design assigning five (5) birds per replicate for each treatment throughout the entire egg laying phases in which each treatment was replicated three (3) times. This study revealed that increased inclusion levels of BSFLM in layers diets led to a significant increase in egg weight (F4, 20 = 15.241, P < 0.001) and yolk weight (F4, 20 = 8.068, P < 0.001). BSFLM inclusion in the layers diet did not significantly alter the n-6 (omega-6) and n-3 (omega-3) ratio (F4, 20 = 1.438, P =0.258). The monounsaturated fatty acids (MUFA) content significantly increased with increasing levels of BSFLM (F4, 20 = 41.054, P =< 0.001). Inclusion of BSFLM in the layers diet contributed to a significant increase in MUFA content and the egg weight, Haugh unit and shell thickness collectively improving the quality of the eggs. MSc in Food Science and Technology 2026-05-20T00:00:00Z http://localhost/xmlui/handle/123456789/6946 Nutrient Composition of Two Cricket Species (Scapsipedus icipe and Gryllus bimaculatus), and Effect of Extrusion Process Optimization on Nutritional, Functional and Sensory Properties of Maize-Cricket Porridge Flour Murugu, Dorothy Kanorio Globally, there is growing interest in integrating cricket flour into plant-based foods to combat nutritional insecurity. However, data on the nutrient profiles of Scapsipedus icipe and Gryllus bimaculatus—the most widely consumed cricket species in Kenya— remains limited. Incorporating crickets into food matrices and using extrusion may impact the nutritional and functional properties of the formulated products. Optimal extrusion parameters for maximizing nutrient yield from various cricket species remain undefined. This study aimed to (i) determine the nutrient and anti-nutrient phytochemical composition of the two cricket species and compare them with published records of key animal and plant sources (ii) develop a nutritionally balanced maize-cricket formulation and evaluate the effect of extrusion on nutrient and functional properties of the formulated product using existing extrusion conditions (iii) determine the sensory attributes of porridges prepared with extruded and non-extruded maize-cricket flour blends and (iv) optimize the extrusion process parameters for attainment of optimal product in extruded maize-cricket porridge flour blends. Standard analytical methods were used to determine the nutrient composition of both cricket species. Maize-cricket blends were formulated using adult cricket powder, maize flour, and sugar. These were optimized using Minitab 20 software to meet the daily protein requirements of children aged 5-12 years. Three formulations containing 10%, 15%, and 20% cricket powder were prepared and processed both by extrusion and non-extrusion methods and samples subjected to nutritional and functional analysis. A semi-trained panel of 46 participants evaluated the sensory attributes of the porridge samples using a 9-point hedonic scale. Response Surface Methodology (RSM) through Box Benhenken design and the extreme vertices model of Mixture Design were employed to optimize extrusion process variables (barrel temperature, screw speed, and feed moisture) and formulation respectively, aiming to produce a porridge with significantly higher nutrient content from blends of S. icipe and G. bimaculatus with standard maize flour. Both cricket species, S. icipe and G. bimaculatus, demonstrated comparable protein content (56.8-56.9%) to animal sources and higher amino acid profiles to plant-based proteins. Their protein digestibility (80-88%) was similar to common plant foods but slightly lower than animal proteins. The cricket species were notably rich in essential minerals like iron, zinc, and potassium, significantly surpassing plant and animal sources. Calcium content was comparable to most sources, except kidney beans and eggs. Both cricket species offered higher levels of riboflavin, thiamine, and folic acid compared to conventional sources. Vitamin A was significantly higher in S. icipe compared to G. bimaculatus. Notable amounts of polyunsaturated fatty acids were found in (S. icipe (24.71%) and G. bimaculatus (19.16%), alongside saturated and monounsaturated fatty acids. Physicochemical properties of oils from both species revealed high similarity across most parameters, including refractive index, specific gravity, peroxide value, and saponification value (P = 0.1047, 0.0774, 0.3581 respectively). However, a highly significant difference was observed in acid values, with S. icipe (2.19 ± 0.36 mg KOH) exhibiting more than double the acidity of G. bimaculatus (1.10 ± 0.01mg KOH; P < 0.001). Additionally, G. bimaculatus demonstrated a slightly higher solidification temperature range (2–7°C) compared to S. icipe (2–5°C). These results suggest that while the primary chemical stability and density of the two lipids are comparable, they differ significantly in their free fatty acid content and thermal xxii behavior. Analysis of anti-nutritional factors in S. icipe and G. bimaculatus revealed significant differences in most phytochemical markers (P < 0.05). G. bimaculatus contained significantly higher levels of phytates (10.33 ± 6.00 mg/100g vs. 3.85 ± 0.44 mg/100g; P = 0.012) and tannins (1.56 ± 1.08 mg/100g), which were not detected in S. icipe (P = 0.003). Conversely, S. icipe exhibited a significantly higher concentration of total polyphenols (65.00 ± 1.79 mg/100g) compared to G. bimaculatus (48.00 ± 4.49 mg/100g; P = 0.021). No significant difference was observed in oxalate concentrations between the two species (P = 0.076). These findings indicate that while G. bimaculatus possesses a more diverse anti-nutritional profile, S. icipe is richer in total polyphenolic content. Extruded porridge flours incorporating cricket powder were significantly more desirable in terms of appearance (P = 0.003), texture (P = 0.001), and mouthfeel (P = 0.028) compared to non-extruded counterparts. Consumer preference was most desirable with the addition of cricket powder at a 10% enrichment level. Taste, texture, and thickness were the most influential sensory attributes with a desirability rate of 21%, 26.6% and 17.2% respectively. The addition of cricket powder at different levels resulted in varying changes in the proximate composition, functional, and pasting properties of the porridge. While some properties like ash, dry matter, and P2 temperature remained unchanged (P = 0.657, P = 0.295, P = 0.851 respectively), protein digestibility increased at the 10% substitution level. Hydration properties improved, and bulk density decreased with increasing cricket powder levels. Extrusion reduced pasting properties, except for P2 temperature (P = 0.851). Optimal extrusion conditions were determined to be a barrel temperature of 120°C, a screw speed of 40 rpm, and a feed moisture content of 12%. Under these conditions, blends with S. icipe achieved a higher protein content (7.7%) with greater reliability (93.8% (d=0.9377)) compared to G. bimaculatus blends (5.8%) with a reliability of 43.5% (0.4347). In conclusion, both cricket species in this study were found to have significant levels of protein, minerals, fat and vitamins. When compared to conventional food sources using the Kenya Food Composition Tables, both species were shown to have either similar or higher values for protein, mineral, vitamins and fat. The extruded corn-cricket porridge evaluated in this study containing 16.52 g/100g of crude protein with an in vitro digestibility of 54.5%, provides 9.00 g of digestible protein per 100 g serving. Based on WHO/FAO (WHO/FAO/UNU, 2007) guidelines, this represents a substantial contribution to the daily requirements of school-going children, meeting approximately 49.1% of the RNI for a 5-year-old and 23.5% for a 12-year-old. Therefore, it is recommended to policy makers as a viable option to be added into the food basket for school meals in Kenya. Ph in Food Science and Nutrition 2026-05-11T00:00:00Z http://localhost/xmlui/handle/123456789/6934 Heavy Metals and Pathogen Content on Soil, Water and Produce in Urban Agriculture of Nairobi City Njenga, John Ng’ang’a Urban and peri-urban agriculture in Nairobi City County (NCC) is growing as a means of income generation, employment, nutrition and food security. However, environmental health risks outweigh urban agriculture practices in the city, as evident from widespread pollutant sources such as garbage dump site heaps, burst raw sewage pipes, contaminated wetlands, industrial effluent, and motor vehicle exhaust. Consumers are increasingly aware of the importance of buying safe food, and therefore urban agriculture practitioners must be informed on the safety status of their produce in order to adjust to good agricultural practices and take full advantage of the easily accessible consumer food market. The objectives of this research were to assess heavy metal incidence in inputs and food crops for urban farms in eastern zone of Nairobi, determine microbial incidences in food crop produce from farms, determine differences in element uptake by the crops, and to examine influence of environmental quality of the surrounding spaces on crop produce safety. A purposive sampling of farmers who grew any of the three target crops namely arrowroot (Colocasia esculenta L.), kale (Brassica olerasii var.Acephala L.) and tomatoes (Lycopersicon esculentum Mill.) was conducted of which ninety five farmers were identified. To focus on the critical regions of the city and with the guidance of Sub-County Agricultural Officers, three sub-counties of Starehe, Kamukunji and Kasarani, in the Eastern part of Nairobi City County were selected. Farm plots that met the criteria for the three target crops were identified (Starehe 4, Kamukunji 7 and Kasarani 4). From each of the 15 farm plots, samples of tomatoes, arrowroots, kales, water and soil were obtained with three replications per farm, following standard procedures for sample collection. Farmer’s immediate environment (neighbourhoods) were classified according to three pollution levels low, moderate, and high that were classified based on source and type of inputs and the condition of the environment surrounding the farm plot. Contents of cadmium, manganese, zinc and lead were analysed using Atomic Absorption/Flame Emission Spectrophotometer. Microbial analysis on irrigation water and the three produce was done to test for presence of salmonella, shigella and Escherichia coli bacteria. One way ANOVA was applied (i) to examine differences in means of heavy metals between locations and to compare transfer factor (TF) index of the crops and (ii) to examine differences on occurrence of the pathogenic microbes. Elements that were above allowable limits in the crops were Cd, Mn, Pb and Zn in arrowroots; Cd and Mn in kales and Cd, Mn and Pb in tomatoes. Cadmium content was highest in farm plots within Kasarani (2.44±0.86 mk/kg) and was significantly different from other two locations (p<0.05, Tukey HSD test). Between the neighbourhood qualities, heavy metal contents were different but not significant (p>0.05) between classes. The mean TF index for the heavy metals decreased in the order Cd>Pb>Zn>Mn. A transfer factor index of > 1 for cadmium was recorded in arrowroots, kales, and tomatoes. Overall, the highest mean of E.coli bacteria count was recorded in arrowroots at the Kamukunji sub-county (P=0.002). Between neighbourhoods, E.coli was significantly higher in irrigation water and arrowroots in the low-quality neighbourhoods (p<0.05). Kamukunji had the highest occurrence of Salmonella in irrigation water and arrowroots at 40%. There was no significant difference between neighbourhood classes in the prevalence pattern of Salmonella. The sub-county also had the highest prevalence of Shigella in irrigation water, at 20%. The overall mean rate of occurrence of Shigella was highest in irrigation water and in kales, at a rate of 17% in both cases. xiii Compared to the other sub-counties, Kasarani had a much higher prevalence of Shigella in tomatoes with a significant difference in distribution pattern (p=0.001). Based on FAO/WHO standards, the measured heavy metal contents were high enough to cause health risk concerns. Produce from areas designated as of low environmental quality was not necessarily contaminated, as perceived. Urban agriculture producers in Nairobi need technical risk reduction technologies and legislative support to guarantee quality produce and valuable participation in the urban food system framework. It is recommended that future studies diversify crop types and localities and enhance collaboration between stakeholders. MSc in Horticulture 2026-05-04T00:00:00Z